Recent developments in internal combustion engine technology have led to newly developed MultiAir® engine technology. Engines with MultiAir® technology are different from traditional internal combustion engines in that they comprise a valvetrain with electro-hydraulic valve actuation, instead of a traditional camshaft, to provide full control over the intake air valves' lift and timing. This has provided improvements in vehicle fuel consumption, emissions, and power.
Currently, however, MultiAir® engines may take additional time to start-up after extended periods of non-use, e.g., storage. Because of the construction of the MultiAir® actuator assembly, a number of clearances exist where hydraulic fluid (i.e., engine oil) can very slowly leak out of internal pressure and reservoir chambers. The space previously occupied by the hydraulic fluid subsequently becomes occupied by air. During engine start-up and operation, the hydraulically actuated valves require hydraulic fluid to function. If air has replaced some of the hydraulic fluid in the chambers, the air must be purged and hydraulic fluid must reenter the chambers before valve actuation and engine start-up can occur.
The current MultiAir® system uses two tiny orifices to purge air from the hydraulic fluid pressure chambers during MultiAir® engine start-up and to circulate hydraulic fluid during MultiAir® engine operation. The orifices are located in a plate which closes the top of the hydraulic fluid mid-pressure chambers. These orifices, however, contribute to the leaking of hydraulic fluid when the engine is not used. The orifices of the current MultiAir® system also limit ventilation of unwanted air from the chambers at engine start-up. As a result, when hydraulic fluid leaks out of the MultiAir® system and is replaced by air during extended periods of MultiAir® engine non-use, engine start-up can be delayed, requiring additional time (i.e., longer than normal) for engine start-up. In severe instances of hydraulic fluid leakage, the MultiAir® engine may not start.
The orifices of the current MultiAir® system also do not prevent the siphoning of air back into the hydraulic fluid pressure chambers upon engine shut-down. This further adds to the delayed start-up of the engine because more air must be purged from the system.
Accordingly, there is a need and desire to provide an apparatus that improves and facilitates the start-up of a MultiAir® engine after long periods of standstill and non-use.